The present disclosure relates to systems, devices, and methods for demodulation and decoding in optical communications systems.
Fiber optic channels in network communications systems are widely deployed and are considered effective for data transmission, allowing relatively high bandwidth data communication. Optical fiber is typically flexible and can be bundled in cables. It is often used for long-distance communications, because light propagates through the fiber with little attenuation compared to electrical cables. Typical present day commercial optical fiber systems transmit data at 10 or 40 Gbps. Each fiber can carry multiple independent channels, each using a different wavelength of light in a technique known as wavelength-division multiplexing (WDM).
Increased data transmission rates may be desirable as demand for bandwidth increases. However, in fiber optic systems, as data rates increase various optical phenomena begin to manifest and act to limit data transmission rates. For example, optical effects from chromatic dispersion (CD), polarization mode dispersion (PMD), and polarization dependent loss (PDL) begin to have a significant impact on the data transmission rate. Forward error correction (FEC) schemes are often used to send redundant data to address these issues, as well as others.
Many current architectures rely on hard-decision FEC schemes. Although soft-decision FEC schemes are used effectively in other areas of communications, there are implementation and other challenges in high speed optical communications.